JPS63128884A - Television conference system - Google Patents

Abstract

PURPOSE:To store the previous frame condition by its own displaying surface, to eliminate a frame memory and to prevent the generation of flicker by using a displaying element having a data holding function to a display. CONSTITUTION:A display unit provided at the tip to transfer image data compressed by a coding processing with a line is composed of a decoder 11, a display 12 to use the displaying element having a data holding function at a displaying surface itself and a driver 13 to drive the display. The display 12 is composed of a displaying device consisting of a light source and a ferroelectric liquid crystal cell and a driver to drive the displaying device. The ferroelectric liquid crystal has a bistable characteristic in the molecular orientation condition, the stable condition occurs once, then, the crystal has a character to hold the stable condition even when the driving condition is removed. Thus, by using the displaying element having the previous frame condition to the display 12, the previous frame condition can be stored by its own displaying surface, the frame memory is eliminated and the flicker generation can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a system in which a plurality of people hold a televised conference by connecting images and sounds via a line, and particularly relates to a system that connects images and sounds via a line and uses a display device having a data retention function. The present invention relates to a video conference system equipped with a video conference system.

[Summary of the Disclosure] This specification and drawings describe a video conferencing system that connects one image and audio via a line, which eliminates frame memory by providing a display that uses a display element that has a data retention function on the display surface itself. , discloses a technique for preventing the occurrence of flicker.

[Prior Art] In recent years, a television conference system has been proposed that connects different locations using images and sounds and allows multiple people to hold a conference without being present together.

Figure 4 is a block diagram showing an example of such a television conference system, in which each conference room has a configuration and is connected to each other by a line. This is, for example, a video camera, and numeral 42 is a code system, which is a circuit that performs code processing, and compresses image data transmitted over a line. 43 is a video display device;
It is mainly used to display images transmitted from other conference rooms, and in some cases, to display input from the imaging system 41 in the own room. 44 is a drive circuit that drives the display device 43, and 45 is a decoding circuit that decodes the image data compressed by the code system 42. 46 is a line interface for inputting and outputting compressed image data and audio data through the line. 4
7 is a sound reproduction system that reproduces audio information sent through one line, and 48 is a sound collection system that collects audio information!
and sends it to the line.

Conventionally, in this type of video conferencing system,
Sequential transmission of all moving image data increases communication costs due to the large amount of data, so in order to reduce costs, it is common to compress image data and use it for transmission as compressed data. In this case, compression using interframe correlation is generally used, and only information about changes from the previous frame image is compressed and used as data for transmission. This type of compression is disclosed in Nikkei Electronics, April 23, 1948 issue (volume 341), pages 197-203, and Japanese Patent Application Laid-Open No. 60-229484.

[Problems to be Solved by the Invention] In the above case, since the frame difference is given by the difference between frames, it is a necessary condition on both the coding side and the decoding side to memorize the state of the previous frame. However, conventionally, the display device itself uses a raster scanning type display device.

It is necessary to scan all images for each frame, and as shown in the conventional example in FIG. The data from the decoder 54 must be differentially processed by the adder 55 and the multiplexer 56, which complicates one circuit and also causes flickers.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a television conference system equipped with a display device capable of transmitting only change information from the previous frame without having a frame memory. With the goal.

[Means for Solving the Problems] Means for solving the above problems will be explained using FIG. 1 corresponding to the embodiment. This is a video conference system that transmits data between terminals, and has a decoder 11 that decodes image data, a driver 13 that is a driving means that drives a display using the decoded image data, and a data retention function on the display surface itself. At the end is a display device consisting of a display 12 using a display element, a readout circuit 14 as a readout means for reading data from the display surface, and an adder 15 as a rewriting means for rewriting image data using the read data. In particular, the present invention is a television conference system in which a ferroelectric liquid crystal cell is suitably used as a display element having a data retention function.

[Function] The display used in the present invention is a display element that has a data retention function, and has the property that the display surface itself remembers the state of the previous frame, which is not necessary in conventional systems. The display frame memory that was previously used can be omitted, and when driving, the transmitted difference data only needs to be displayed on the display as new data in addition to the previous data, making frame correlation compression possible. In addition to being compatible with the above, it also prevents flicker from occurring.

[Embodiment] FIG. 1 is a block diagram showing an example of the configuration of a video conference system according to the present invention. In FIG. 1, the display device is installed at the end of the line for transmitting image data compressed by code processing, and includes a decoder 11 that decodes the image data and a drive means that drives the display using the decoded image data. A driver 13, a display 12 that uses a display element that has a data retention function on the display surface itself, a readout circuit 14 that is a readout means that reads data from the display surface, and a rewriting device that rewrites image data using the readout data. A ferroelectric liquid crystal cell is used as a display element having a data holding function.

Since the display element used in the present invention has the property that the display surface itself remembers the state of the previous frame, the frame memories 53a and 53b for the display section as shown in the conventional example in FIG. is no longer necessary and is very well suited for systems that transmit compressed data.

Next, we will explain the display. The display used in this example consists of a light source, a display device consisting of a ferroelectric liquid crystal cell having a structure as shown in FIG. 2, and a driver for driving this display device. The ferroelectric liquid crystal used in 0 display devices has bistability in the state of single-molecule orientation, and once a stable state is created, it has the property of maintaining that stable state even if the driving state is removed. This method is disclosed in Japanese Patent Application Laid-Open No. 156047/1986 and "Electronic Materials" February 1986 issue, pages 72-77.

FIG. 2 is a diagram showing the structure of a ferroelectric liquid crystal cell. Second
In the figure, striped transparent electrodes 22a, 22b and an alignment film 23 are formed on glass substrates 21a, 21b, and the two substrates are arranged to face each other so that the transparent electrodes cross each other. Furthermore, a ferroelectric liquid crystal 25 and a spacer 24 defining a cell gap are sealed between the substrates 21a and 21b, and one peripheral portion is sealed with a sealing material 26. Polarizing plates 27 in a crossed Nicol state are provided on both sides of the element with such a cell structure, and one image information is transmitted from the light source (
It is observed from the upper part of the figure by light Io from a source (not shown). FIG. 3 schematically shows the arrangement of electrodes on the display surface of the cell, and is indicated by 22b in the figure.
113114 IIs l... is a transparent electrode on the substrate 21b side, S I + S2 shown in 22a
+ S3 *S4 + 55 +... is the board 21a
This is the transparent electrode on the side.

I 1 (i*1.2.3.
) and S > (j-1, 2, 3, . . . ) intersect with each other, each becoming a display pixel. Here, as mentioned above, a pair of linear polarizers (polarizing plates) are arranged on both sides of the element in a cross Nicol relationship with the ferroelectric liquid crystal in between, so a potential difference is applied between II and 55. By applying an electric field to a display pixel, the orientation of ferroelectric liquid crystal molecules at that pixel position is determined, and the light 1 from the light source is
It is possible to control whether or not o is transmitted to the display screen.

The readout circuit 14 and its method for reading out the data stored on the display screen may be of a known type, and the added difference data that has been transmitted is added to the previous data in the adder 15 and then read out again to the driver as new data. 13 and displayed on the display 12.

Note that in order to rewrite only a part of one display surface, a method disclosed in, for example, Japanese Unexamined Patent Publication No. 60-31120 may be used.

[Effects of the Invention] As explained above, according to the present invention, by using a display element having a data retention function in a display,
A configuration that does not require a frame memory for display is possible, and it is sufficient to drive the display element only for changes, making it compatible with frame correlation compression and preventing flicker.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a structural diagram of a ferroelectric liquid crystal cell used for the display screen, Fig. 3 is a schematic diagram of electrode arrangement with respect to the display screen, and Fig. 4 5 is a general block diagram of a television conference system, and FIG. 5 is a block diagram of a conventional display device. 11, 45.54: Decoder, 12, 43.51: Display. 13, 44.52: Driver (driving means), 14: Reading circuit (reading means). 15.55: Adder (rewriting means), 41: Imaging system, 42: Code system, 53: Frame memory, 56: Multiplexer.

Claims (2)

[Claims] (1) In a television conference system that transmits image data compressed through encoding processing along with audio data to each end via a line, there is a decoder that decodes the image data, and a display based on the decoded image data. a display using a display element having a data retention function on the display surface itself; a reading means for reading data from the display surface; and a rewriting means for rewriting the image data using the read data. A television conference system comprising a display device at a terminal end thereof. (2) The television conference system according to claim 1, characterized in that a ferroelectric liquid crystal cell is used as a display element having a data retention function.